Fibre mats

Abstract

A fibre mat ( 1 ) comprises inorganic fibres ( 3; 5 ) held in a flocculated binder system ( 4 ), the binder system comprising less than 12 w/w % of the mat. The binder-fibre flocs ( 3, 4 ) may be held together with relatively long inorganic fibres ( 5 ). A film cover layer ( 6 ) may be present.

1. A fibre mounting mat to support a monolith in an exhaust system, the mat comprising inorganic fibres held in a flocculated binder system, the binder system comprising less than 12% by weight (w/w %) of the mat, wherein the inorganic fibres comprise a plurality of relatively short fibres with a length of from 0.01 mm to 5 mm and a plurality of relatively long fibres with a length of from 8 mm to 16 mm. 
     
     
       2. A mat according to  claim 1 , wherein the relatively long fibres are from 10 mm to 14 mm long. 
     
     
       3. A mat according to  claim 1 , wherein the relatively long fibres are from 11 mm to 13 mm long. 
     
     
       4. A mat according to  claim 1 , wherein the relatively long fibres have a mean diameter of from 1 μm to 10 μm. 
     
     
       5. A mat according to  claim 1 , wherein the relatively long fibres comprise up to 30% by weight (w/w %) of the inorganic fibres. 
     
     
       6. A mat according to  claim 5 , wherein the relatively short fibres are a mixture of alumina and inullite fibres. 
     
     
       7. A mat according to  claim 5 , wherein the relatively long fibres comprise 5% by weight (w/w %) or less of the inorganic fibres and the binder system comprises 5% by weight (w/w %) or less of the mat. 
     
     
       8. A mat according to  claim 7 , wherein the relatively short fibres comprise alumina or mullite fibres. 
     
     
       9. A mat according to  claim 1 , wherein the relatively long fibres comprise silica. 
     
     
       10. A mat according to  claim 1 , wherein the relatively long fibres interconnect flocs of binder and relatively short fibre. 
     
     
       11. A mat according to  claim 1 , further comprising a surface layer applied to one or both major surfaces thereof. 
     
     
       12. A mat according to  claim 11 , wherein the total organic content of the mat is in the range of 5% by weight (w/w %) or less, and the relatively long fibres comprise up to 5% by weight (w/w %) of the inorganic fibres. 
     
     
       13. A combination of a mat according to  claim 1 , a monolith about which the mat is wrapped and a can in which the wrapped monolith is inserted or insertable, the coefficients of static and kinetic friction, measured between the surface of the mat and the cans are respectively less than 0.5 and 0.4. 
     
     
       14. A method of manufacturing a fibre mounting mat for supporting a monolith in an exhaust system, the method comprising the steps of forming a slurry of relatively short inorganic fibres having a length of from 0.01 to 5 mm and relatively long inorganic fibres having a length of 8 mm to 16 mm in a liquid carrier, adding flocculated binder to the slurry, stirring to form binder-fibre flocs and drying the flocculated slurry, and
 wherein the mat comprises the inorganic fibres held in a flocculated binder system, and the binder system comprises less than 12% by weight (w/w %) of the mat. 
 
     
     
       15. A method according to  claim 14 , further comprising, during the drying step, compressing the flocculated slurry to a predetermined density. 
     
     
       16. A method of manufacturing a fibre mounting mat for supporting a monolith in an exhaust system, the method comprising the steps of forming a slurry of relatively short inorganic fibres having a length of from 0.01 mm to 5 mm in a liquid carrier, adding binder to the slurry, flocculating and stirring the mixture to form binder-fibre flocs; adding, with stirring, relatively long inorganic fibres having a length of from 8 mm to 16 mm to the binder-fibre flocs and drying the flocculated slurry ,and
 wherein the mat comprises the inorganic fibres held in a flocculated binder system, and the binder system comprises less than 12% by weight (w/w %) of the mat. 
 
     
     
       17. A method according to  claim 16 , comprising, during the drying step, compressing the flocculated slurry to a predetermined density. 
     
     
       18. A method according to  claim 16 , comprising applying a surface layer to the mat either prior to drying or after drying. 
     
     
       19. A method according to  claim 16 , comprising applying a surface layer to the mat after drying. 
     
     
       20. A method of forming a mounting mat for supporting a monolith in an exhaust system with increased laminar shear strength at a given fibre gap bulk density, the method comprising forming a mat from relatively short inorganic fibre-binder flocs and interconnecting at least some of the flocs with relatively long inorganic fibres having a length of from 8 mm to 16 mm, the relatively short fibres having a length of from 0.01 mm to 5 mm,and
 wherein the mat comprises the inorganic fibres held in a flocculated binder system, and the binder system comprises less than 12% by weight (w/w %) of the mat. 
 
     
     
       21. A method according to  claim 20 , comprising applying a surface layer to the mat either prior to drying or after drying.